Optical power isolator

Abstract

An optical isolator for improving the isolation between an optical source and a transmission link in an optical communications system. The optical isolator comprises a tapered lens including a core region and surrounding cladding material. The core region can be fabricated from graded or step index glass and the cladding can be fabricated from glass or polymer material. The core region can also be fabricated from graded or step index polymer material with the cladding fabricated from polymer material. An opaque disk of carbon-filled epoxy is deposited on the large diameter end of the optical isolator to further enhance isolation.

I claim: 
     
       1. A device for improving the isolation in an optical communications system between a coherent optical source and a transmission link comprising a tapered lens and including a core region and cladding material, said tapered lens having a large diameter input end and a small diameter output end wherein said core region exhibits a higher index of refraction than said cladding material such that light coupled into said input end is transmitted at low insertion loss to said output end, and light entering said output end and which feeds back to said coherent optical source is reduced. 
     
     
       2. The device of claim 1 further comprising an opaque disk deposited on the center of the input surface of said large diameter input end of said tapered lens. 
     
     
       3. The device of claim 1 wherein said tapered lens includes a glass core having a step refractive index distribution and it is surrounded by a glass cladding material. 
     
     
       4. The device of claim 1 wherein said tapered lens includes a glass core having a step refractive index distribution and is surrounded by a polymer cladding material. 
     
     
       5. The device of claim 1 wherein said tapered lens includes a polymer core having a step refractive index distribution and is surrounded by a polymer cladding material. 
     
     
       6. The device of claim 1 wherein said tapered lens includes a glass core having a graded refractive index distribution and is surrounded by a glass cladding material. 
     
     
       7. The device of claim 1 wherein said tapered lens includes a glass core having a graded refractive index distribution and is surrounded by a polymer cladding material. 
     
     
       8. The device of claim 1 wherein said tapered lens includes a polymer core having a graded refractive index distribution and is surrounded by a polymer cladding material. 
     
     
       9. An efficient optical communication system comprising: a coherent optical source;   a transmission link; and   a tapered lens disposed between said coherent optical source and said transmission link, and having a large diameter input end and small diameter output end, and further including a core region and surrounding cladding material wherein light coupled into said input end from said optical source is transmitted with low insertion loss to said output end, and light entering said output end from said transmission link is attenuated before feeding back to said optical source.   
     
     
       10. The device of claim 9 wherein said coherent optical source includes at least one semiconductor laser diode. 
     
     
       11. The device of claim 9 wherein said optical source includes at least one semiconductor laser diode having an optical fiber pigtail. 
     
     
       12. The device of claim 9 wherein said transmission link includes at least one optical fiber. 
     
     
       13. The device of claim 9 wherein said transmission link includes collimating optics components. 
     
     
       14. An optical isolator for improving the isolation between a coherent optical source and a transmission link in an optical communications systems comprising a tapered lens, said tapered lens having a large diameter input end and a small diameter output end, and including a central cladding zone, a transmission region surrounding said central cladding zone, and an outer cladding zone surrounding said transmission region wherein said transmission region exhibits a higher index of refraction than either of said central and outer cladding zones to enhance light propagation in the transmission region. 
     
     
       15. The optical isolator of claim 14 wherein said tapered lens further comprises an opaque disk centered on said central cladding zone on said large diameter input end.